1. Field of the Invention
The present invention relates to a tree felling and grappling head and in particular to a tree felling and grappling head for attachment to a boom of vehicle used in forestry or logging operations. The head has grapple arms which can grip around the trunk of a tree, and a saw that can cut through the tree trunk being gripped by the grapple arms.
2. Description of Related Art
A tree felling head is attached to the boom of a vehicle and used in the forestry industry. Felling heads have been used for severing the tree stem from its stump and laying the severed stem on the ground for later extraction from the forest by other means. The cutting tools used in felling heads may include circular saws, discs, guillotines and chainsaws. In the United States of America and Canada, circular saws and discs are more commonly used because tree size is relatively small. Chainsaw cutting mechanisms are typically used for tree felling operations in New Zealand where average tree sizes are significantly larger.
Felling heads are also used for grappling or shovelling operations in which felled stems are picked up off the ground and repositioned to facilitate more efficient or cost effective extraction to a site where the stems will ultimately be loaded onto transport, for example trucks or railway cars.
U.S. Pat. No. 5,390,715 describes an apparatus for cutting and pruning trees. A grapple and saw assembly 23 includes a grapple assembly 29 and a saw assembly 50. The saw assembly is attached to the output shaft 48a of a rotary hydraulic motor 48. The motor and the grapple assembly are attached to a frame 24. The saw assembly includes a chain saw hydraulic motor 51. A positioning mechanism permits the saw assembly to rotate through an arc of 360 degrees independently of movement of the grapple assembly.
U.S. Pat. No. 6,374,877 describes a bar saw feller buncher and method of felling trees. Harvesting arms 18, 20, 22 are pivotally attached to a frame 12 of a bar saw felling head 10. A bar saw 14, includes a saw bar and cutting chain is driven by a motor 16. A rotary or linear hydraulic actuator may rotate the bar saw through 90 degrees about the axis of the chain saw drive motor 16, or a different axis, to move the saw between a home position, in which the saw is housed in an open-sided box 40, and a cocked position.
U.S. Pat. No. 7,311,126 and corresponding New Zealand patent 532008 describe a grapple head assembly with a grapple 1 and a cut-off chain saw 30. A hydraulic saw drive motor 20 is mounted in a head portion 20 of the grapple. The saw bar 42 pivots about the saw drive sprocket 25, which is preferably coaxial with a pivot axis of a jaw 4 of the grapple.
The effectiveness of grappling or shovelling by prior art felling heads is limited due to the position of the saw box that houses the cutting mechanism.
In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents or such sources of information is not to be construed as an admission that such documents or such sources of information, in any jurisdiction, are prior art or form part of the common general knowledge in the art.